When driving a vehicle at high speed, it is dangerous to look at anything other than the road directly ahead. It is especially dangerous to look down at the dashboard display to read the tachometer or speedometer; not only may the vehicle travel a considerable distance while the gaze is averted, but the eyes take time to refocus when the driver looks down at the dashboard and then up to the road again. During that refocusing time critical events may take place that the driver may not fully perceive because of the delay in focusing. Further, the conventional numerical displays (whether digital or analog) require some time for interpretation. This is because the numbers symbolize and signify something and require at least a moment of cognition to ascertain what action, if any, to take in view of the information provided. Accordingly, racers using conventional tachometers occasionally simply memorize needle locations or make an educated guess as to actual engine RPM by considering other factors, such as engine sound.
Current known solutions to avoid the gaze-shifting problem include mounting the tachometer on the hood of the car or mounting the tachometer on top of the dash within the driver's general line of sight but, due to their sheer size, tachometers mounted on dashboards obstruct vision in some measure. Whether the tachometer is mounted within the driver's general line of sight or moved to one side, the driver's gaze is required to be shifted or averted from the road to view it.
Another proposed solution has been to “clock” the tachometer. “Clocking” entails rotating the tachometer in its housing, such that when the tachometer is indicating redline, the needle points straight up or in another preferred direction.
Other proposed solutions were the addition of shift lights to simplify the interpretation of shift points, or to add a pre-set indicator needle to the tachometer display. Adding a preset needle provides the tachometer with adjustability for a specific redline, so when the moving needle aligns with the pre-set indicator needle, the engine's redline or shift point is more easily determined.
These previous solutions improve, but do not eliminate, the gaze-shifting problem. Additionally, these solutions also do not make the determination of redline, or engine RPM, significantly easier for the driver to assess.